finally, airplane mode trick worked. if you disable the wifi too quick, it will say can't connect with the error code and if you wait too long, it would say up to date. so just try different wait times. for me i think it was about 3-4 seconds.

if you get the message you can't check for updates you are pulling the cable too fast, if it says you are up to date you are leaving it in too long. I started counting 1 Mississippi, and if I got the can't check for updates, I did it again and counted to 2. I did this until I got the message I was updated (4 Mississippi) then pulled when I got to 4 Miss (about 3.25 seconds I guess) and it worked.

Wierd, I updated, and it wasn't 7.8. It was some update for phones without a camera button. So I went to do the cable trick a second time and this time I had to pull the cable after about one second. I'm now loading 7.8. AT&T Lumia 900.

When you say disable WiFi, you mean my laptop? My phone is already in airplane mode and connected via USB.

ATT
Nokia Lumia 900
Windows 7

You want to disconnect your computer from the internet. If you are using a wired connection you can either pull out your ethernet cable or disable the network adapter. If your computer is connected to the internet through wifi then you can disable wifi.

I had wifi off on phone and airplane mode. Using Corleones method, I kept switching from update to any other and turning off wifi on the computer. I really didn't think it would work. About the 5th try it did. Good luck! Did not update to 7.8, I have 8783.12. Okay, leave the wifi on the computer off, ohhhhhh. I only received 2 updates. But I am done, thank you forum!

Finally got the update with the tips from previous posts...
(Lumia 900/ AT&T)

Remember to:

(1) Put your phone to airplane mode
(2) Unplug the cable physically! (Turning off wifi did not work for me)

Other than that, if you see "can't check for update @!#$#@", that means you're unplugging it too soon, and if you're seeing "your phone is up to date", then as mentioned in previous posts, you didn't do it quick enough. There seems to be a specific unplugging timing for you to get the update, not too fast, but not too slow either.

Be patient guys!

I took YINK TKs advise. I was patient and finally notified of an update. The process took around 1/2 hour. But I noticed something weird. It just said "Nokia Update for windows phone". (no os # or anything.) Then, in the description it had two items: 1) Provides support for phones without a physical camera button. 2) Provides other windows phone improvements. TO MY SHOCK, THE UPDATE FINISHED "SUCCESSFULLY", AND NO NEW START SCREEN OR ANYTHING OTHER VISIBLE!!! NOW I JUST WANT TO SMASH THE PHONE. ANY HELP?????

Took a few tries but I got the Zune trick to work. It's on the first update (phones without physical camera buttons). Hopefully it goes through all the updates without me having to do the Zune trick each time.

Took a few tries but I got the Zune trick to work. It's on the first update (phones without physical camera buttons). Hopefully it goes through all the updates without me having to do the Zune trick each time.

You have to. First time, I have to wait about 3 to 4 seconds. Second time, I have wait only about 1 second.